Combustion device and water heater

A combustion device comprising:

• an inner case that houses three or more burners;
• and
• a gas distribution unit assembled to the inner case, the gas distribution unit including three or more nozzles, a main flow passage, and at least two distribution flow passages, the three or more nozzles ejecting a fuel gas to the respective burners, the fuel gas being introduced to the main flow passage, the at least two distribution flow passages branching the fuel gas from the main flow passage to each of groups of a plurality of the nozzles mutually different in number of the nozzles, wherein
• the number of the burners to be combusted is switchable by switching whether to supply the fuel gas or not to each of the distribution flow passages,
• in the gas distribution unit, at an upstream end of the distribution flow passage with a large number of the nozzles, an inflow port into which the fuel gas is allowed to flow from the main flow passage is formed, and a solenoid valve configured to open and close the inflow port is disposed,
• a connecting flow passage is formed such that the connecting flow passage communicates between a downstream side with respect to the inflow port of the distribution flow passage with the large number of the nozzles and a communication port provided at an upstream end of the distribution flow passage with a small number of the nozzles,
• an additional solenoid valve configured to open and close the communication port is selectively mountable at the upstream end of the distribution flow passage with the small number of the nozzles,
• when the additional solenoid valve is mounted, a state of supplying the fuel gas to only the distribution flow passage with the large number of the nozzles by opening the solenoid valve and closing the additional solenoid valve and a state of supplying the fuel gas to the two distribution flow passages by opening the solenoid valve and opening the additional solenoid valve are mutually switchable, and
• when the additional solenoid valve is not mounted, a state of supplying the fuel gas to the two distribution flow passages by opening the solenoid valve and a state of not supplying the fuel gas to the two distribution flow passages by closing the solenoid valve are mutually switchable.